The CSS3 Speech module and CSS2 aural style sheets — or at least, parts of them — are experimentally supported in Presto Opera (possibly up to and including 12.10, but not including 15 and later, which are based on Blink, which doesn't implement them at all).
Note that aural style sheets were obsoleted in CSS2.1 and later resurrected as the CSS3 Speech module; the old spec is just there for historical reference. Considering that the Speech module is already a Candidate Recommendation (CR) as of 2012, it's unlikely any new browser will ever implement aural style sheets, so you can forget about testing those and just focus on code that is based on the new spec.